Cap Sensor-Part II

[bigkim100]

SEEBN MY FIRST CAP SENSOR POSTING SO THAT THIS WILL MAKE SENSE
The other way that I was thinking would be to imbed temperature sensors into the walls of the plastic container that would sense the temperature of the walls of the container. The theory is that the sensor at the 1/2in to 1in level SHOULD be a different temperature than the walls of the empty part of the container. The sensors could be diodes, and they would be hooked up to a op-amp, to hopefully trigger when there is a difference between the full level and the empty level. maybe with a huge amount of hysterisis, the sloshing between the sensors would be ignored .
Whatcha think???

 

[philba]

what happens when the entire system reaches thermal equilibrium?

I would think weight is a fairly accurate way to do this.

You might be able to use capacitance. 2 metal foil or plates on opposite sides of the tank. the capacitance between those 2 plates is proportional to the amount of dielectric between them. the tank may be too large for this, though. Some automobile gas gauges use this.

 

[dknguyen]

Scale

Just stick the tank on a scale. it's not a very big tank. It's also probably more simple and reliable than the other methods you can think of.

Philba:
So...that's how you would use capacitance to measure fluid levels...I also think it's too far though unless high voltages were used or very accurate sensors.

 

[HarveyH42]

Realy too little information. 'Sloshing', is this for a mobile (vehicle not cellphone) project. The contents and use or action? Are you trying to determine when your beer can is almost empty, and time pop open a fresh one? Would that be pretty obvious (unless you've had a few to many already), then again shouldn't be driving anyway... Will the fluid be left to evaporate, and you need to refill the container?
Temperature sensing, what material is your tank? An aluminum beer can may not provide a big temperature difference at fluid level, unless the fluid is much warmer or colder than the ambient temperature. Basically, if the can is at room temperature, and the fluid is at room temperature (hate warm beer)... Over time the temperature will equalize.

 

[stevez]

I am wondering if you can't use sound. Tap on the side or bottom of a container and it often sounds different depending on fluid level.

 

[dknguyen]

SIgnal

Hearing would take more signal processing though (well, not really, it would just require knowing which frequencies to filter). YOu would have to be able to pick out the sound caused by tapping the tank and separate it from the sound of splashing inside the tank. And tapping is more mechanically bulky, especially if you want to measure the level of fluid instead of just a threshold. If you used vibrations then it would get harder to separate splashing from the tank sounds.

I think the sloshing is from water splashing as it's poured in.